[css-flexbox] "Determine the flex container’s used cross size" step needs to take min/max size into account

Right now, the Flexbox ED has the following:
  #  15. Determine the flex container’s used cross size:
  #   * If the cross size property is a definite size, use that.
  #   * Otherwise, use the sum of the flex lines' cross sizes.

I'm pretty sure that last bullet-point needs to have something like this
appended:
", clamped to the flex container's cross-axis min-size / max-size
properties"

Without that change, I'm pretty sure this section is implicitly saying
to disregard "min-height" & "max-height" on auto-height horizontal flex
containers. (which seems undesirable)

Thanks,
~Daniel